Plasticization of gelatin



2,904,434 PLASTICIZATION OF GELATIN Kirby M. Milton, Rochester, N.Y.,assignor to Eastman Kodak Company, Rochester, N.Y., a corporation of NewJersey N'o Drawing. Application May 31, 1957 Serial No. 662,564

7 Claims. (Cl. 96-94) This invention relates to the plasticization ofgelatin and'ofphotographic gelatin emulsions by means of lower alkylesters of ethylene bis glycolic acid.

Some materials such as glycerin or other polyols are known to plasticizegelatin probably because of their possible interaction with gelatin ortheir hygroscopicity. The use of suflicient amounts of those polyols toefiectively plasticize photographic emulsions at low humidities may beundesirable because of the physical and sensitometric properties theyexhibit at high humidities and tempera.- tures. It has been previouslyrecognized that certain polyethylene glycols may be useful in silverhalideemulsions to improve anti-static properties, sensitometricproperties and coatability. However, there has never been any statementin the art pointing out any unusual value of these glycols for gelatinplasticizing purposes.

One object of my invention is to provide gelatin coating compositionswhich give coatings having good flexibilities. Another object of myinvention is to plasticize photographic gelatin layers and photographicfilms contaifiiiig those layers. A further object of'rny invention is toplasticize gelatin employed for photographic purposes'without anyadverse physical or sensitometric effct's as might result from manycurrently knowngelatin plasticiiers'.

I have discovered that the above objects may be obtained byincorporating in gelatin coating compositions lower alkyl esters ofethylene bis glycolic acid in the amount of 40% based on the weight ofthe gelatin. The esters which have been found to be particularlysuitable for this purpose are the dimethyl, diethyl and di- (ethoxysubstituted ethyl) esters of ethylene bis glycolic acid. In those caseswhere the coating is dried under Very drastic conditions, it isdesirable to-have as much as. 15%v (based on the weight of the gelatin)of the ester in. the. gelatin composition. With less drastic dryingconditions, smaller amounts of the ester are used. The methyl'ester ispreferred in that it appears to be useful in all situations which areencountered in the formation of -gelatin coatings. I have found that upto 40% of the plasticizer in accordance with my invention (based on theweight-of the gelatin) can be tolerated in gelatin coatings withoutgiving riseto softness or tackiness at high humiditie's. The followingexamples illustrate my invention:

Example 1 Several gelatin skins and gelatin-silver halide photographicemulsion skins were prepared by coating out aqueousvsolutions comprising8% of photographic gelatin and the indicated percentages of plasticizeronto stripping type plates so that skins of 4 mm. thickness wereobtained; The skins were cured at 70 F. and 70% R.H. until dry, werestripped from the plates, slit to widths of 15 mm. and conditioned to 70F. and 20% R.H. Folding endurance was tested with an MIT fold testerusing a tension of 1 kg. and jaws of 0.0155 inch radius Patented Sept.15, 1059 of curvature with a separation of 0.01 inch. The followingresults were obtained:

MIT folds at 20% R.H.

Percent 1 Plasticlzer Gelatin Emulsion skins skins 0 None of] Ethylenebis (methyl glycolate) O 1 5 rl n 20 dn 1 Parts per 100 parts ofgelatin.

Example 2' Tackiness Brittleness, Sward 70 F., 15% R.H. RockerOoefiicient oi 709 EL, ,irictiome'mul- Per- Plasticizer 80% sion toemulsion cent R.H..

g Wedge; MIT Damp.-. 70 F4, 70." F

in. folds ing 50% 70% time, RLHI' 'RJH.

sec.

o None .28 o 41 .39. 1.34

20:..- Et ylenebis I (methyl glycolate) .18 l9 38. .33. 7.39

1 This value is believed to be a measure of tackiness and/or softness.Increased tackiness and/or softness is shown by a decrease in SwardRocker damping times and an increase in the coefiicient of frictionvalues. Increased flexibility is shown by a decrease inwedge-brittlenessivalue and by an increase in MIT fold value.

Example 3 Compositions were prepared from a negative type photographicemulsion, plasticized with various contents of plasticizer. Theresulting emulsions were coated on cellulose acetate support and driedat F. wet bulb and 120 F. dry bulb temperature. The films obtained weretested and the results were as follows:

Tackiness Brittleness, Sward v I 70 F., 15% R.H. Rocker; Coefficient ofI 70- F;, friction, emul Per- Plasticizer sionto emulsion cent R.H.

Wedge, MIT Damp-. 70 F;, 70F.,. 1n. folds ing 50% 70% time, RH .RJEL

sec.

0 None; 0.22 1 44 15. Ethylene bis- (methyl glycolate 12 17 43 .16 20 42.18 20 40 .16 25 43 .19 24 40 Glycerin .19 16' 22 Example 4 Skins wereprepared from gelatin and from a silver halide photographic emulsion inthe manner described in Example 1 using various plasticizers. The skinsso obtained were tested and the results were as follows:

MI'l folds at 70 F., 20% RH. Percent Plastlcizer Gelatin Emulsion sheetssheets N one 24 14 20 Ethylene bis (methyl glycolate) 33 56 20 Ethylenebis (ethyl glycolate) 71 20 Ethylene bis (Z-methoxyethylglycolate). 73138 20 Ethylene bis (2 (2- methoxyethoxy) ethyl glycolate) 77 135Example 5 Plasticized negative-type photographic emulsions were coatedonto cellulose acetate film base in the same manner as described inExamples 2 and 3. The resulting product was tested and the resultsobtained were as follows:

Photographic films were prepared by the method described in Example 2.Those films were tested and the;

following results were obtained:

Tackiness Brittleness, Sward 70 F., 15% RH. Rocker, Coefficient of 70F., friction, emul- Per- Plasticizer 80% sion to emulsion cent RH.

Wedge, MIT Damp- 70 F., 70 F., in. folds ing 50% 70% time, RH. R31.

sec.

0 None 0.23 0 48 0. 47 0. 44 20..-- Ethylene bis (methyl glycolate) 1315 47 i 49 46 20 Ethylene bis (2- methoxyethyl glycolate) 21 0 45 39 4120 Ethylene bis (2-(2- methoxyethoxy) thyl 23 0 47 34 .36 19 6 23 52 82The use of the plasticizers in accordance with my invention in amountsup to as much as 40%, based on the weight of the gelatin, in gelatincoating compositions was found to have no derogatory effect upon theproperties of the coatings prepared from those compositions or onphotographic emulsions containing those plasticizers. If thoughtdesirable, gelatin compositions instead of being plasticized entirelywith the plasticizers described in accordance with my invention, may beplasticized with mixtures of one or more of these compounds withcompatible glyeols providing 50% of the plasticized material is an esterof ethylene bis glycolic acid. As examples of mixtures which might beuseful are compositions of ethylene bis (methyl glycolate) with glycerinand mixtures with polytriethylene glycols providing at least 50% of theplasticizer employed is the ester of ethylene bis glycolic acid.

Ordinarily the plasticizers will be added to the gelatin solution beforethe formation of a coating thereof al- 1 though plasticization of agelatin layer can be accom- V R being selected from plished byimbibition of plasticizer from an aqueous solution thereof. However,where a multi-layer coating is desired, plasticization can beaccomplished by incorporating a plasticizer in accordance with myinvention into one of the gelatin layers which plasticizer migrates intolayers adjacent thereto. Ethylene bis(glycolic acid) is also known underthe name (ethylenedioxy) diacetic acid, HOOCCH OCH CH OCH COOH.

I claim:

1. A gelatin coating composition comprising an aqueous solution ofgelatin containing therein 5-40%, based on the weight of the gelatin, ofan ester having the formula:

OOHQOOOR in which formula R is a substituent selected from the groupconsisting of methyl, ethyl and alkoxyethyl.

2. A silver halide-gelatin photographic emulsion which contains therein540%, based on the weight of the gelatin, of an ester having thefollowing structural formula:

0011200011 i CH5 OCHEOOOR ethyl and alkoxyethyl.

3. A gelatin coating composition comprising an aqueous solution ofgelatin containing approximately 20%, based on the Weight of thegelatin, of a compound having the formula:

OCHZCOOR OCHnOOOR R being selected from the group consisting of methyl,ethyl and alkoxyethyl.

4. A gelatin coating composition comprising an aqueous solution ofgelatin having therein 540%, based on the weight of the gelatin, ofethylene bis(methyl glycolate).

5. A gelatin coating composition comprising an aqueous solution ofgelatin having therein 5-40%, based on the weight of the gelatin, ofethylene bis(ethy1' glycolate). V

6. A gelatin coating composition comprising an aqueous solution ofgelatin having therein 540%, based on the Weight'of the gelatin, ofethylene bis (methoxyethyl 'glycolate) 7. A silver halide-gelatinphotographic emulsion containing therein 540%, based on the weight ofthe gelatin of ethylene bis(methyl glycolate).

References Cited in the file of this patent UNITED STATES PATENTS1,757,482 Seel May 6, 1930 the group consisting of methyl,

1. A GELATIN COATING COMPOSITION COMPRISING AN AQUEOUS SOLUTION OFGELATIN CONTAINING THEREIN 5-40%, BASED ON THE WEIGHT OF THE GELATIN, OFAN ESTER HAVING THE FORMULA: